Semiconductor device



Sept. 27, 1966 w. H. PARKER SEMICONDUCTOR DEVICE Filed June 26, 1961 INVEN TOR. Warren H. Parker United States Patent 3,275,904 SEMICONDUCTORDEVICE Warren H. Parker, Phoenix, Ariz., assignor to Motorola, Inc.,Chicago, 11]., a corporation of Illinois Filed June 26, 1961, Ser. No.119,731 3 Claims. (Cl. 317-234) This invention relates in general topower transistors of the alloyed junction type, and particularly to sucha transistor with the semiconductor unit portion of the device mountedintermediate the emitter and base contact conductor posts for thetransistor and in a substantially straight line position within thedevice.

The present invention is related to the structure and method of assemblyof Kelley applications Serial No. 847,718, and 847,735 now Patent No.3,061,766, which were filed October 21, 1959, and October 21, 1959,respectively, and is also related to Ackerman applications Serial No.83,794 and 83,795, now Patents Nos. 3,153,275 and 3,153,750 and filedJanuary 19, 1961, and January 19, 1961, respectively. It provides animprovement in structure and method of assembly over prior devicesemploying a base with a threaded mounting stud centrally thereof, andserving as one electrical connection from the semiconductor unit, whileemitter and base connections are spaced away from the unit and disposedrespectively on opposite sides thereof. In the present invention thesemiconductor unit is mounted on a pedestal portion aligned with thestud, and connections are made to the base and emitter contact orelectrode portions on the semiconductor unit by two interconnectedpre-stamped met-a1 connectors. The latter are dropped in place for suchconnections without independent jigging, but are positioned accuratelyrelative to the contact portions on the semiconductor unit by conductoror post portions extending upwardly from the base and comprising emitterand base connections for the device. Interlocking structure of theconnectors when placed on the post portions and unit originallypositions them in a straight line across such semiconductor unit, andthen permits the pieces to settle into a final assembled position duringheating and soldering of the assembly without any change of positionthereof relative to these points lying in the straight line.

With this interconnected and articulated connecting means for thesemiconductor unit and conductors or posts, there is assurance that thepieces are in the proper position without any jigging independent of thepower transistor structure itself, and high speed of assembly withuniformity and ruggedness of the finished product is assured.

Referring to the drawings:

FIG. 1 is a general perspective view of the power transistor;

FIG. 2 is an enlarged plan view of the power transistor without itscover and with the elements in assembled position but not soldered;

FIG. 2a shows the elements of this subassembly in an exploded view, withthe base member turned counterclockwise 90 from the position of FIG. 2;

FIG. 3 is an enlarged cross-sectional view of the power transistorsubassembly taken along line 3--3 of FIG. 2, except that the assembly inthis figure has been soldered or fused together and is ready forencapsulation;

FIG. 4 shows an enlarged plan view of the top of the semiconductor unit;

FIG. 5 is an enlarged bottom view of the largest electrical connectormember;

FIG. 6 is an enlarged top view of the smallest of the two interconnectedelectric connector members;

FIG. 7 is a cross-sectional view of the first electrical connectormember taken along line 7-7 of FIG. 5, and in enlarged size; and

3,275,904 Patented Sept. 27, 1966 FIG. 8 is a cross-sectional view ofthe semiconductor unit taken along line 8-8 of FIG. 4.

Referring more particularly to the drawings, the device is shown in FIG.1 substantially in actual commercial size with a cover 10 and a base 11.Two conductor or post portions 12 and 12a, a threaded mounting stud 13,and an orientation post 14 project downwardly from the base. The cover10 is cold welded to the base 11 at the annular flange 16 (FIG. 3).

The semiconductor unit 17 is the heart of the power transistor, and isshown in the enlarged plan view of FIG. 4, and in section in FIG. 8. Itstop face contains a central, circular base electrode 21. Completelysurrounding the base electrode 21 is an annular ring emitter electrode22, and completely surrounding the latter electrode is an annular ringbase electrode 23. The electrodes 21, 22 and 23 are concentric. Thesemi-conductor die 24 (FIG. 8) is germanium in a commercial embodimentof the invention. The collector electrode 26 appears on the bottom faceof the complete unit.

The remaining elements of the assembly of FIG. 2, and as shown in detailin FIG. 20, will be referred to before describing the method ofassembling the device, and such elements include the connector 27 (FIG.5) which will ultimately electrically interconnect the base electrodes21 and 23 on the semiconductor unit and a corresponding post 12a. Thesecond connector identified by the reference character 28 (FIG. 6) willextend between the ring emitter electrode 22 and the post or conductor12.

Although the spacing between the concentric electrodes on the face ofthe semiconductor die 24 is minute, relatively speaking, an insulatingseparation must be maintained, and this is accomplished in theconnectors by a stepped configuration shown particularly in FIGS 2a, and7. The base connector 27 comprises a central enlarged portion with anannular right-angled flange 29 serving the double function of assistingin the positioning and maintaining of the semiconductor unit 17 on thebase 11 during assembly, and being ultimately soldered or fused to thering base electrode 23 for the electrical connection. An integralhorizontal tongue 31 extending from one end portion of the elongatedconnector is ultimately fused to the center base electrode 21. As isshown in FIG. 3 this is out of contact with the ring emitter electrode22. The one-piece connector 27 is interlocked during assembly through anupstanding tongue 32 with the connector 28, as will be described, andend portions with apertures 33 and 33a complete this element. Theapertures 33 and 33a fit over conductors 12 and 12a.

The second one-piece connector 28 has a C-shaped prong 34 to engage thering emitter electrode 22, and an aperture 36 to receive the tongue 32on the first connector to interlock them during assembly. The connectoris positioned in assembly with the aperture 37 receiving the post 12.

The full assembly function for the structure of the connectors will besubsequently explained, but we will first complete the description ofthe remaining elements. The base 11 comprises the integral stud portion13 which also can be separable if desired, and a pedestal 38 inalignment with the stud portion. Apertures 41 and 41a receive thefeedt-hroughs 12 and 12a or posts or conductors, as they are also calledherein, and the aperture 42 (the base in FIG. 2a is rotated so it showsthis aperture in the sectional portion) receives the orientation post14. The feedthroughs each have a flange 43 and 43a, respectively, whichdetermines the position to which the connectors settle in the finalassembly and heating, and the soldering of the feedthroughs, base, andconnectors together is accomplished with soldering rings 44 placed aswill be explained.

In the assembly process, the base 11 (FIG. 2a) is these holes (FIG. 2).

placed on a moving conveyor belt in an upright position. A solder ring44 is placed above and concentric with hole 42, and orientation post 14is dropped through that solder ring and into the hole 42. Solder rings44 are placed above and concentric with holes 41 and 41a, and the postsor feedthroughs 12 and 12a are dropped into The semiconductor unit 17 isplaced on and concentric with pedestal 38, with the ring electrodesfacing upwards (FIG. 3), and with the collector electrode 26 on thepedestal top surface. The first connector member 27 is dropped down overthe posts 12 and 12a and the unit 17. The posts 12 and 12a pro jectupwards through the corresponding apertures 33 and 33a in the firstconnector member 27 (FIG. 2), and the central portion with the flangedrim 29 surrounds and further locates the unit 17 on the pedestal 38. Thesecond connector member 28 is then dropped over the post 12 (on the leftin FIG. 2), and in this placing and positioning it interconnects withthe prong 32 at the aperture 36. In this manner the second connectormember is aligned along a straight line that joins the posts orcondoctors 12 and 12a and the semiconductor unit 17.

Thus, the unit 17 is positioned concentrically with the pedestal 34,lies on a straight line between the two pins 12 and 12a,- and iscontained by the circular flange or rim 29 of the first connector member27.

FIG. 3 is a sectional view through the entire subassembly and showsclearly the manner in which the parts readily fit together, and areultimately secured in position. Here the unit 17 can be seen located atthe center of the structure and resting on pedestal 38. The firstconnector 27 runs between posts 12 and 12a, and the prong 32, which ispart of the first connector 27, projects upward through the smalleraperture 36 in the second connector member 28 thereby providingalignment for the two connector members and with the posts 12 and 12a.

Following the assembly of the various parts, the entire subassembly ofFIG. 2 is run through a high temperature firing furnace to melt thesolder, and the posts 12 and 12a, and the orientation post 14 aresoldered to the base 11. At the same time the unit 17 is fused to thepedestal 38 at the collector electrode 26, the ring base electrode 23(FIG. 4) is fused to the flanged portion 29, and the prong portion 34 ofthe second connector 28 is fused to the emitter electrode 22. The tongue31 on the connector 27 is fused to the center base electrode. Bothconnector members are soldered to the posts 12 and 12a on which theyrest. The firing step causes the solder as Well as the electrodematerial to melt, and fusion or soldering of the elements isaccomplished.

Meanwhile, the conveyor belt on which the assembly has been moving allof the time, carries the assembly in the condition shown in FIG. 3 outof the furnace, all of the parts cool, and the meltable material securesthe connector members, the unit and the base together by means ofsoldered or fused joints, and establishes the desired electricalconnections.

The steps of placing the various parts on the base 11 without the needfor independent locating fixtures are straightforward and can be donequickly. The connector members 27 and 28 readily drop into place overthe posts and the seimconductor unit. The interlocking feature betweenthe connectors provides positive alignment of the .connectorsintermediate the posts 12 and 12a, and the connectors maintain the unit'17 in the desired position the reference character 30 on one side ofthe extension, I using a small tool. Enough rigidity remains in themember 27 to permit it to be properlyassembled into the structure. Afterthe entire subassembly has been put through the firing furnace and allthe solder connections have cooled and are fixed ,(as for FIG. 3), acurrent is passed between the posts 12 and 12a. This current flowsthrough the unsevered side 3110 of the web and enough heat is generatedto cause that side to burn open. This removal of the webs 30 and 30aeliminates any emitterto base short between the posts 12 and 1201.

Thereafter, the assembly of FIG. 3 is cleaned and the cover 10 issecured to the base at the flange 16. This latter securing is not a partof the present invention.

The round-style power transistor package such as shown in FIG. 1 is adesirable type of package and is used commonly in industry. By locatingthe stud 13 at the center of the device package, excellent thermal andelectrical contact to the surface on which the transistor is mounted canbe obtained. As can be seen in FIG. 3, the pedestal portion 38 islocated centrally with respect to the base 11 and this pedestal isaligned and is concentric with the threaded stud 13. With the unit 17soldered directly to the top face of the pedestal, heat generated in thesemiconductor unit during operation of the transistor, can be veryefficiently conducted into the base 11 and out through the device towhich the transistor is mounted.

The over-all height of the transistor can be kept to a minimum becauseof the limited space which the first and second connector membersrequire. This efficient use of vertical space can be seen in FIG. 3. Thestepped portion of the left end of the first connector member 27provides a vertical space or separation between the first such connectormember and the second connector member 28, so that there is no shortcircuit to the electrodes on the unit 17. When the final web portion 30ais severed by the current, then, even though the left end portion, asviewed in FIG. 3, of connecto-r 27 remains on the post 12, and theconnector 28 connects the post 12 and the emitter electrode, there is noshort circuit between the different electrodes on the semiconductorunit.

The secure and compact manner in which the connecto members, thesemiconductor unit, and the base member are joined, provides a veryrugged, and mechanically reliable structure. Because of theconfiguration of the two connector members as previously described, thesoldered connections between the ends of the connector members and theposts 12 and 12a are at the same height above the surface of the base11, and this permits the posts to be of exactly the same configurationand dimensions.

In solving the problem of devising highly efficient assembly methods fora power transistor package where the unit assembly and the emitter andbase posts are in one straight line, the first and second connectormembers of -the present invention allow straightforward, rapid assemblysteps with self-jigging features which are well suited to massproduction conveyor-belt assembling, and all of the soldered connectionscan be formed at one time. The firing operation and subsequent coolingprovides a semiconductor assembly with a compact group of parts stronglybonded together.

I claim:

1. In a semiconductor device having a base support structure with a pairof conductor members protruding from one side of said structure, and asemiconductor die unit supported by said structure and positionedbetween said conductor members, the combination including a firstconnector member making a connection to the semiconductor die unit andelectrically connected to one of said conductor members, a connectorpart derived from said first connect-or member and secured to the otherof said conductor members, said first connector member and saidconnector part being physically and electrically separate from eachother in the final device but extending in a straight line between saidconductor members and initially being one piece to facilitate thealignment of said first connector member relative to said semiconductordie unit and said base support structure in the manufacture of saiddevice, a second connector member electrically con nected to said otherconductor member and to said semiconductor die unit, said secondconnector member and said connector part having portions in overlappingrelationship relative to each other with means interlocking the same tofacilitate the alignment of said second connector member relative tosaid semiconductor die unit and said base support structure in themanufacture of said device, and solder joints connecting said first andsecond connector members to the respective conductor member.

2. In the semiconductor device of claim 1, said first connector membercomprising a longitudinally extending element having an annular portionengaging and fused to a corresponding annular portion of thesemiconductor die unit, and having an extension from said annularportion connected to said one conductor member, said extention having atongue connected to said semiconductor die unit Within said annularportion, and said connector part being in line With said extensionportion but on the opposite side of said annular portion.

3. A semiconductor device including in combination, a base supportstructure having a pair of conductor members projecting from one surfacethereof and a semiconductor die unit supporting area on said surfacespaced from each conductor member and locate-d centrally between saidconductor members with said conductor members and said area representingthree points in a substantially straight line, a semiconductor die uniton said supporting area having an electrode portion on one side thereofin contact with said base support structure at said area and said dieunit having a pair of concentric ring electrodes on the other sidethereof and a center electrode within the innermost of said ringelectrodes, a first connector member having an apertured portion fittingover a corresponding conductor member and having an enlarged portion incontact with the outer ring electrode of said die unit and a prongedportion in contact with the center electrode of said die unit, aconnector part derived from said first connector member and having anapertured portion fitting over the other of said conductor members, saidfirst connector member and said connector part being physically andelectrically separate from each other in the final device but extendingin a straight line between said conductor members and initially being inone piece to facilitate the alignment of said first connector memberrelative to said semiconductor die unit and said base support structurein the manufacture of said device, a second connector member having anapertured portion fitting over said other conductor member and having anextension in contact With the inner ring electrode of said semiconductordie unit, said second connector member and said connector part havingportions in overlapping relationship relative to each other with meansinterlocking the same to facilitate the alignment of said secondconnector member relative to said semiconductor die unit and said basesupport structure in the manufacture of said device, and solder jointsconnecting said connector members and said connector part to thecorresponding conductor members.

JOHN W. HUCKERT, Primary Examiner.

GEORGE N. WESTBY, Examiner. A. S. KATZ, R. SANDL'ER, AssistantExaminers.

1. IN A SEMICONDUCTOR DEVICE HAVING A BASE SUPPORT STRUCTURE WITH A PAIROF CONDUCTOR MEMBERS PROTRUDING FROM ONE SIDE OF SAID ARMATURE, AND ASEMICONDUCTOR DIE UNIT SUPPORTED BY SAID STRUCTURE AND POSITIONEDBETWEEN SAID CONDUCTOR MEMBERS, THE COMBINATION INCLUDING A FIRSTCONNECTOR MEMBER MAKING A CONNECTION TO THE SEMICONDUCTOR DIE UNIT ANDELECTRICALLY CONNECTED TO ONE OF SAID CONDUCTOR MEMBERS, A CONNECTORPART DERIVED FROM SAID FIRST CONNECTOR MEMBER AND SECURED TO THE OTHEROF SAID CONDUCTOR MEMBERS, SAID FIRST CONNECTOR MEMBER AND SAIDCONNECTOR PART BEING PHYSICALLY AND ELECTRICALLY SEPARATE FROM EACHOTHER IN THE FINAL DEVICE BUT EXTENDING IN A STRAIGHT LINE BETWEEN SAIDCONDUCTOR MEMBERS AND INITIALLY BEING ONE PIECE TO FACILITATE THEALIGNMENT OF SAID FIRST CONNECTOR MEMBER RELATIVE TO SAID SEMICONDUCTORDIE UNIT AND SAID BASE SUPPORT STRUCTURE IN THE MANUFACTURE OF SAIDDEVICE, A SECOND CONNECTOR MEMBER ELECTRICALLY CONNECTED TO SAID OTHERCONDUCTOR MEMBER AND TO SAID SEMICONDUCTOR DIE UNIT, SAID SECONDCONNECTOR MEMBER AND SAID CONNECTOR PART HAVING PORTIONS IN OVERLAPPINGRELATIONSHIP RELATIVE TO EACH OTHER WITH MEANS INTERLOCKING THE SAME TOFACILITATE THE ALIGNMENT OF SAID SECOND CONNECTOR MEMBER RELATIVE TOSAID SEMICONDUCTOR DIE UNIT AND SAID BASE SUPPORT STRUCTURE IN THEMANUFACTURE OF SAID DEVICE, AND SOLDER JOINTS CONNECTING SAID FIRST ANDSECOND CONNECTOR MEMBERS TO THE RESPECTIVE CONDUCTOR MEMBERS.